Rotary mowers are in common use for mowing lawns and, as is well known in the art, some rotary mowers are especially constructed or equipped with special blades and/or other mulching attachments for mulching or shredding the material being cut during mowing. The present invention is particularly concerned with improvements in rotary mowers of the type equipped with a rotary mulching blade or blades in addition to the usual rotary cutting blade. Such type of mower is disclosed, for example, in Niemann U.S. Pat. No. 2,956,386, wherein a pair of vertically spaced rotary coaxial mulching blades are disposed rearwardly of a rotary cutting blade within a common mower housing. The use of vertically spaced coaxial blades or set of blades for cutting and/or mulching vegetation is further disclosed in other U.S. patents, such as, Sewell Pat. No. 2,809,488; Bovee Pat. No. 2,760,327; Whitney Pat. No. 2,734,327; and Pohels Pat. No. 2,843,991, for example. The vertically spaced coaxial blades or sets of coaxial blades disclosed in each of the aforementioned patents are driven to rotate in a common direction.
A rotary mower having coaxial sets of lower and upper cutting blades which rotate in opposite directions from each other is disclosed in Stauffer U.S. Pat. No. 3,129,549, wherein the upper set of cutting blades is adapted to rotate in shearing relation to the lower set of cutting blades in a horizontal plane so as to produce scissor-like cutting actions. The lower and upper sets of blades of the latter patent are respectively fixedly mounted on lower portions of a vertical shaft and a hollow hub encircling the shaft. The shaft and hub extend upwardly through a wheeled framework, are mounted for rotation in a relatively complicated bearing arrangement, and have respective upper portions with respective coaxial pulleys thereon, which pulleys are engaged by respective upper and lower runs of a driven common endless belt. Such an arrangement for driving the lower and upper cutting blades in opposite directions has drawbacks, such as, only a relatively small segment of each of the latter pulleys; e.g., substantially less than 180 degrees thereof, is engaged by the respective run of the belt in any given instant, thus requiring that the belt be highly tensioned in order to prevent slippage of such runs on the coaxial pulleys. Also, with both runs of the endless belt being positioned above the base framework of the mower as in the Stauffer patent, the thus exposed upper and lower runs of the endless belt, and the exposed upwardly projecting idler pulley supporting means associated therewith, present a constant hazard to an operator.